Energy generation devices relying on the motive power of a fluid, nominally water, driven by an expanding vapor have been explored and developed for many decades.
Kershaw in U.S. Pat. No. 6,739,131 discloses a “Combustion-Driven Hydroelectric Generating System” which exploits the explosive force of expanding combustion gasses to drive a metered slug of liquid into a pressurized vessel. The liquid or gas within the vessel provides pressure to drive a stream of liquid that can be used to actuate a pelton wheel. The rotational mechanical energy of the pelton wheel is then converted to electricity.
Tobber in U.S. Pat. No. 4,201,049 similarly describes a method of using expanding combustion gasses to supply energy to a liquid which can subsequently drive a pelton wheel.
Domdey in U.S. Pat. No. 4,394,815 describes a “Turbo generator Using High Pressure Vapor”, a device which utilizes high pressure vapor injected into an existing water current to transmit additional energy to the water. The stream is diverted towards a hydraulic turbo pump wherein its kinetic energy is converted into mechanical energy to be used for generating electricity.
Prueitt et al. in U.S. Pat. No. 7,021,900 also discloses using an external heat source to drive a boiler to produce heated vapor. The resulting vapor can be used to accelerate slugs of liquid the force of which can be used to pump fluids or drive a pelton wheel to generate electricity.
All of the aforementioned patents describe devices that are capable of delivering kinetic energy in the form of a moving fluid without the need for mechanical pistons or gearboxes. Disadvantageously, U.S. Pat. Nos. 6,739,131 and 4,201,049 require direct contact between the combustion products, the mechanisms for combustion (valves, ignition sources, etc.), and the liquid to be propelled. This makes for a complicated design for the combustor. The combustion products can also contaminate the propelled liquid which can degrade the performance of the engine by the gradual accumulation of undesirable compounds and residues.
Aforementioned U.S. Pat. Nos. 4,394,815 and 7,021,900 both use external sources of heat that eliminates the problems associated with combustion. In the former patent however, a source of constantly flowing water must be present and this limits the range of applications. In the latter patent, the design of a u-shaped “acceleration tube” and presence of a “check valve” limits the ultimate efficiency of the device. The geometry and size of the “acceleration tube” also limit the velocity of the fluid stream and the frequency with which it can be ejected.
All of the aforementioned approaches, with exception of U.S. Pat. No. 4,394,815, suffer from losses of energy due to the fact that the propulsive combustion products or vapors are not allowed to fully expand as they accelerate their respective liquid pistons. Useful energy is therefore given up to the environment.